Reuse empty views when opening a new document

XiEditor/AppDelegate.swift

@@ -20,6 +20,9 @@ class AppDelegate: NSObject, NSApplicationDelegate {
     var dispatcher: Dispatcher?
     var styleMap: StyleMap = StyleMap()
 
+    /// used internally to force open to an existing empty document when present.
+    var _documentForNextOpenCall: Document?
+
     func applicationWillFinishLaunching(_ aNotification: Notification) {
 
         guard let corePath = Bundle.main.path(forResource: "xi-core", ofType: "")
@@ -46,7 +49,7 @@ class AppDelegate: NSObject, NSApplicationDelegate {
         }
         return nil
     }
-    
+
     func handleCoreCmd(_ json: Any) {
         guard let obj = json as? [String : Any],
             let method = obj["method"] as? String,

XiEditor/Document.swift

@@ -36,6 +36,9 @@ class Document: NSDocument {
 	var pendingNotifications: [PendingNotification] = [];
     var editViewController: EditViewController?
 
+    /// used to keep track of whether we're in the process of reusing an empty window
+    fileprivate var _skipShowingWindow = false
+
     override init() {
         dispatcher = (NSApplication.shared().delegate as? AppDelegate)?.dispatcher
         super.init()
@@ -44,25 +47,46 @@ class Document: NSDocument {
     }
 
     override func makeWindowControllers() {
-        // Returns the Storyboard that contains your Document window.
-        let storyboard = NSStoryboard(name: "Main", bundle: nil)
-        let windowController = storyboard.instantiateController(withIdentifier: "Document Window Controller") as! NSWindowController
+        var windowController: NSWindowController!
+        // check to see if we should reuse another document's window
+        if let delegate = (NSApplication.shared().delegate as? AppDelegate), let existing = delegate._documentForNextOpenCall {
+            assert(existing.windowControllers.count == 1, "each document should only and always own a single windowController")
+            windowController = existing.windowControllers[0]
+            delegate._documentForNextOpenCall = nil
+            // if we're reusing an existing window, we want to noop on the `showWindows()` call we receive from the DocumentController
+            _skipShowingWindow = true
+        } else {
+            // if we aren't reusing, create a new window as normal:
+            let storyboard = NSStoryboard(name: "Main", bundle: nil)
+            windowController = storyboard.instantiateController(withIdentifier: "Document Window Controller") as! NSWindowController
+
+            //FIXME: some saner way of positioning new windows. maybe based on current window size, with some checks to not completely obscure an existing window?
+            // also awareness of multiple screens (prefer to open on currently active screen)
+            let screenHeight = windowController.window?.screen?.frame.height ?? 800
+            let windowHeight: CGFloat = 800
+            windowController.window?.setFrame(NSRect(x: 200, y: screenHeight - windowHeight - 200, width: 700, height: 800), display: true)
+        }
+
         self.editViewController = windowController.contentViewController as? EditViewController
         editViewController?.document = self
         windowController.window?.delegate = editViewController
-
+        self.addWindowController(windowController)
+
         Events.NewTab().dispatchWithCallback(dispatcher!) { (tabName) in
             DispatchQueue.main.async {
             self.tabName = tabName
             }
         }
-        //FIXME: some saner way of positioning new windows. maybe based on current window size, with some checks to not completely obscure an existing window?
-        // also awareness of multiple screens (prefer to open on currently active screen)
-        let screenHeight = windowController.window?.screen?.frame.height ?? 800
-        let windowHeight: CGFloat = 800
-        windowController.window?.setFrame(NSRect(x: 200, y: screenHeight - windowHeight - 200, width: 700, height: 800), display: true)
+    }
 
-        self.addWindowController(windowController)
+    override func showWindows() {
+        // part of our code to reuse existing windows when opening documents
+        assert(windowControllers.count == 1, "documents should have a single window controller")
+        if !(_skipShowingWindow) {
+            super.showWindows()
+        } else {
+            _skipShowingWindow = false
+        }
     }
 
     override func read(from url: URL, ofType typeName: String) throws {

XiEditor/EditViewController.swift

@@ -81,6 +81,14 @@ class EditViewController: NSViewController {
         document?.sendRpcAsync("insert", params: insertedStringToJson(insertString as! NSString))
     }
 
+    // we override this to see if our view is empty, and should be reused for this open call
+     func openDocument(_ sender: Any?) {
+        if editView?.lines.isEmpty ?? false {
+            (NSApplication.shared().delegate as? AppDelegate)?._documentForNextOpenCall = self.document
+        }
+        NSDocumentController.shared().openDocument(sender)
+    }
+
     // MARK: - Menu Items
     fileprivate func cutCopy(_ method: String) {
         let text = document?.sendRpc(method, params: [])

XiEditor/LineCache.swift

@@ -76,6 +76,13 @@ class LineCache {
             return nInvalidBefore + lines.count + nInvalidAfter
         }
     }
+
+    /// A boolean value indicating whether or not the linecache contains any text.
+    /// - Note: An empty line cache will still contain a single empty line, this
+    /// is sent as an update from the core after a new document is created.
+    var isEmpty: Bool {
+        return lines.count == 1 && lines[0]?.text == ""
+    }
 
     func get(_ ix: Int) -> Line? {
         if ix < nInvalidBefore { return nil }